It was only O'Connell's third game back after returning from the groin injury that he received during Ireland's RBS 6Nations defeat to Scotland in March.
He made his comeback for Young Munster two weeks ago and returned to Magners League action in Munster's 16-9 triumph over Cardiff Blues last weekend.
But just 11 minutes into his cameo appearance after coming off the bench against the Ospreys in Europe the second-row saw red after allegedly elbowing Jonathan Thomas.
And he could be set for another extended absence if he receives a suspension. Under IRB regulations, rule 10.4 (a), striking another player with the elbow carries a minimum two-week suspension and a potential maximum of 52 weeks.
"When I saw the card I was hoping I was colour blind but unfortunately I'm young enough that my eyesight is till good," said Munster head coach Tony McGahan.
"Right now I'm keeping my distance from Paul and giving him some time because he's pretty disappointed."
It would be a major blow to high-flying Munster with a testing festive period approaching with games against Connacht and Ulster.
But Munster are well blessed in the second row department and boast a wealth of riches with the likes of fellow Ireland internationals Donncha O'Callaghan and Mick O'Driscoll within their ranks.
Ahead of his comeback O'Connell had spoke of the competition he faced in the Munster boilerhouse and that strength in depth could now be even more important if the 2009 Lions skipper is handed a ban.
"It's important that I'm patient," said O'Connell. "We have an incredible number of high-class second-rows in the squad.
"There's massive strength in depth in that position and it's important that I get up to the level they're at before I can be considered for selection."
But having successfully returned to the squad, O'Connell may now need extra patience if he is hauled before the disciplinary authorities.
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